<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /* margin: 0 auto;
        要求:块元素,块元素有固定的宽度
        */
        div{
            width: 100px;
            height: 100px;
            border: 1px solid red;
            margin: 0 auto;
        }
        img{
            width: 100px;
            height: 100px;
            border-radius: 50px;;
            box-shadow: 20px 10px 100px yellow;
        }

    </style>
</head>
<body>
<div>
    <img src="images/7.jpg" alt="">
</div>
</body>
</html>